Git workflow - nikolov-tmw/multilingual-wp GitHub Wiki
I've implemented this branching model - "A successful Git branching model" for the plugin's repository. I do find it to be a pretty good one and I would advise you to read the article(if you haven't done so yet) in order to understand how it works.
This model implies that that the master branch will always be at the latest stable release. So if you download the ZIP archive from master, you will get a stable and working version.
If you want to download the latest development version, simply go to https://github.com/nikolov-tmw/multilingual-wp/tree/dev and click on the "Download ZIP" button on the right.
Occasionally there might be other branches, but they will most-certainly be temporary ones and will be removed soon(they might be hotfixes, release branches, feature branches - they are all described in the link on top).
Accompanying every commit on master, a new tagged version will come out. If you want to download a specific version of the plugin, simply go to https://github.com/nikolov-tmw/multilingual-wp/tags and download the version that you want.